Converged communication has been receiving increasing attentions because of its pervasive nature in person-to-person and business-to-business interactions. One critical issue in converged communication is the need of an open and service-oriented paradigm to enable converged communication services, including voice, video, and multimedia, so that communication can be service-oriented and ready to integrate into business transactions.
Service-oriented architecture (SOA) is a major advance in the industry that defines the use of a loosely coupled service description layer to decouple the service interface needed to enable applications from the physical implementation of these services. A key aspect of SOA is that services with their service-oriented interfaces can be accessed independently without knowledge of their underlying platform implementations. SOA defines a framework that allows services to be added, aggregated and re-used in a self-describing and service-oriented manner, so that they are ready to be called and composed in a standard way to perform their tasks, without the services having pre-knowledge of the calling applications, and without the application having or needing knowledge of how the services actually perform their tasks.
Web Service is a technology to enable service-oriented architecture. The service-oriented interfaces in Web Services are defined by the WSDL (Web Service Description Language) descriptions. Web Services are accessed through SOAP (Simple Object Access Protocol) message exchanges. SOAP and WSDL are standard based protocols and languages of W3C, upon which Web Services are defined. SOAP provides an XML-based, extensible message envelope format which can bind to various underlying transport protocols, e.g. HTTP, SMTP, JMS, TCP, etc. This makes Web Services not only loosely coupled with the physical platform implementations, e.g. operating systems, programming languages, etc., but also agnostic to transport protocols that can be used to transport service invocation messages. Therefore, same services can be made available for different platforms and environments. By enabling existing enterprise resources through Web Services, these enterprises can be expanded to provide services to a wider variety of clients. However, Web Services had been used for service integration and not been used as a protocol to establish communication between two endpoints for real-time voice, video, multimedia and converged communication services.
In the past, communication had been a tightly coupled nutshell wrapped by many layers of low-level protocols, and it is difficult to support new applications beyond the basic functions of a standalone device, e.g. telephone. Many protocols were designed based on a bottom-up process to satisfy a pre-defined set of functions which are often at low level and tightly coupled to a particular environment. Each individual protocol may define its own method of extensibility and service integration infrastructure, or decide to leave them open as vendor implementation dependent. This old paradigm is obviously not service oriented, and it has become a bottleneck to support service oriented and distributed communication.